Test apparatus and test method for confirming soil improvement effect

Abstract

To save the labor of measuring work by eliminating the replacement of equipment.SOLUTION: In this testing device 1 for confirming the soil improvement effect, a measuring probe 3 is installed on the tip of a penetration rod 2. In the measurement probe 3, a tip cone 4 used for a dynamic cone penetration test is provided at a tip, an electrode portion 5 including an electrode 6 used for electric logging on an outer peripheral surface is provided above the tip cone 4, an outer diameter of the electrode portion 5 is formed to be smaller than an outer diameter of the tip cone 4, an axial center of the tip cone 4 and an axial center of the electrode portion 5 are eccentric, and the electrode 6 is disposed on the outer peripheral surface on an eccentric side. Since the axial centers of the tip cone 4 and the electrode part 5 are made eccentric and the electrode 6 is arranged on the outer peripheral surface on the eccentric side, the electrode 6 is surely brought into contact with the hole wall surface in the penetration process of the measuring probe 3, and electric logging can be performed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a test device and a test method for confirming the effect of ground improvement by a chemical grouting method in which a chemical or cement-based injection material is injected into the ground as a measure against liquefaction. [Background technology]

[0002] Conventionally, ground improvement work has been carried out using the chemical grouting method, in which a chemical solution made from water glass (sodium silicate) or the like is injected into the ground to strengthen soft ground such as reclaimed land. After construction using the chemical grouting method, a construction confirmation survey is conducted to check whether the chemical solution has been evenly distributed throughout the target ground.

[0003] The most common method for confirming the construction of chemical grouting methods is to evaluate the unconfined compressive strength (qu) of improved soil. However, the unconfined compressive strength of soil improved using chemical grouting is low, at around 50 to 100 kPa, and strength variations can occur depending on the target ground, making it difficult to properly evaluate. In other words, for ground with a low unconfined compressive strength (qu) of around 50 to 100 kPa, disturbances that lead to a decrease in strength are likely to occur when collecting samples or preparing test specimens during follow-up investigations. Furthermore, depending on the target ground, the presence of shells, wood chips, silt, organic soil, etc. in the test specimen can cause strength variations and make it difficult to properly evaluate.

[0004] Therefore, the applicant proposed a new method for confirming the effect of ground improvement using chemical grouting in the following Patent Document 1. Specifically, after ground improvement, a depth distribution map of Nd values ​​showing the relationship between depth and Nd value is obtained by a small dynamic cone penetration test, and a primary effect confirmation is performed to confirm the effect of ground improvement from the increase in the Nd value before and after ground improvement, If the ground improvement effect is not confirmed by the above primary effect confirmation, we proposed a method of conducting electrical logging to measure resistivity by inserting a measurement probe equipped with an electrode into the penetration hole of the small dynamic cone penetration test, obtaining a resistivity depth distribution map showing the relationship between depth and resistivity, and confirming the ground improvement effect from the decrease in resistivity before and after the ground improvement.

[0005] However, the method described in Patent Document 1 below involves a dynamic cone penetration test in which a cone attached to the tip of a rod is penetrated by hammering, then the cone is pulled out and a measurement probe for electrical logging is pressed into the same penetration hole using a pressing device.This means that the equipment needs to be installed twice, first by installing the equipment for penetrating the tip of the cone in the dynamic cone penetration test, and then by installing the pressing device for pressing in the measurement probe for electrical logging.This means that it takes a lot of time to re-install the equipment, and there are issues such as poor measurement efficiency.

[0006] In order to solve this problem, the applicant proposed a new test device for confirming the effect of ground improvement in the following Patent Document 2. Specifically, a tip cone used for dynamic cone penetration testing is provided at the tip of the penetration rod, and an electrode unit equipped with an electrode used for electrical logging is provided above the tip cone. The test device has an eccentric flange at a circumferential position opposite to the circumferential position where the electrode is disposed, the eccentric flange protruding radially outward from the outer diameter of the electrode but not from the outer diameter of the tip cone. After the dynamic cone penetration test, electrical logging can be performed while the penetrated measurement probe is withdrawn. During this electrical logging, the eccentric flange comes into contact with the hole wall of the penetration hole, and sediment accumulates on top of the eccentric flange, pressing the electrode against the hole wall. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-4473 [Patent Document 2] Japanese Patent Publication No. 2023-134012 Summary of the Invention [Problem to be solved by the invention]

[0008] The testing device described in Patent Document 2 above can perform a dynamic cone penetration test during the penetration process and electrical logging during the extraction process for each penetration, but because separate measuring equipment is used for the dynamic cone penetration test and the electrical logging, it takes time to re-install the equipment, which increases the workload of the measurement work.

[0009] Therefore, a main object of the present invention is to provide a test device and a test method for confirming the effect of ground improvement, which eliminates the need to relocate equipment and reduces the labor required for measurement work. [Means for solving the problem]

[0010] In order to solve the above problem, the present invention according to claim 1 provides a test device for confirming the effect of ground improvement, in which a measurement probe is attached to the tip of a penetration rod, The measurement probe has a tip cone used for a dynamic cone penetration test at its tip, and an electrode portion having an electrode used for electrical logging on its outer peripheral surface is provided on the top of the tip cone, an outer diameter of the electrode portion is smaller than an outer diameter of the tip cone, an axis of the tip cone and an axis of the electrode portion are eccentric, and the electrode is disposed on the outer peripheral surface of the eccentric side; A test device for confirming the effectiveness of ground improvement is provided, which is characterized by being able to perform a dynamic cone penetration test and electrical logging simultaneously during the penetration process.

[0011] In the invention described in claim 1, the outer diameter of the electrode portion is smaller than the outer diameter of the tip cone to reduce the effect of peripheral friction during the penetration process of the dynamic cone penetration test. If an electrode were provided on the outer surface of an electrode portion formed with an outer diameter smaller than the tip cone, the electrode would not contact the borehole wall, making electrical logging impossible. However, in the present invention, the axis of the tip cone and the axis of the electrode portion are eccentric, and the electrode is located on the outer surface of the eccentric side. This ensures that the electrode contacts the borehole wall during the penetration process of the measurement probe, enabling electrical logging. In this case, the contact portion of the electrode portion with the borehole wall is linear, thereby reducing peripheral friction during the penetration process of the dynamic cone penetration test.

[0012] In this way, electrical logging can be performed simultaneously with dynamic cone penetration testing during the penetration process, eliminating the need to relocate equipment and reducing the labor required for measurement work.

[0013] As the present invention related to claim 2, there is provided a test device for confirming the effect of ground improvement as described in claim 1, in which the axis of the tip cone and the axis of the electrode part are eccentric to the extent that the outer surface of the electrode part does not protrude radially outward from the outer surface of the tip cone.

[0014] In the invention described in claim 2 above, the range of eccentricity between the axis of the tip cone and the axis of the electrode part is specified in order to reduce peripheral friction during dynamic cone penetration testing while ensuring that the electrode of the electrode part contacts the hole wall surface during electrical logging.

[0015] As the present invention related to claim 3, there is provided a test device for confirming the effect of ground improvement as described in claim 1, wherein the diametrical distance between the outer surface of the tip cone and the outer surface of the electrode part on the eccentric side of the electrode part is 0 to 3 mm.

[0016] In the invention described in claim 3 above, in order to reduce peripheral friction during dynamic cone penetration testing while ensuring that the electrode of the electrode unit contacts the hole wall surface during electrical logging, the range of the diametric separation distance between the outer surface of the tip cone and the outer surface of the electrode unit on the eccentric side of the electrode unit is specifically specified.

[0017] According to a fourth aspect of the present invention, there is provided a test device for confirming the effect of ground improvement according to the first aspect, wherein the measurement interval of the electrical logging is 0.5 to 5 Hz.

[0018] In the invention described in claim 4 above, the measurement interval for electrical logging is specifically specified so that electrical logging can be performed without poor contact between the electrode and the hole wall surface due to vibration of the measurement probe when penetrating by hammer impact in a dynamic cone penetration test.

[0019] As a fifth aspect of the present invention, there is provided a test method for confirming a ground improvement effect using the test device according to any one of claims 1 to 4, A test method for confirming the effect of ground improvement is provided, which is characterized by conducting a dynamic cone penetration test in which the tip cone is driven into the ground by hammering, and simultaneously conducting electrical logging during the same penetration process.

[0020] In the invention described in claim 5 above, a dynamic cone penetration test is performed in which the tip cone is driven into the ground by hammering, and electrical logging is also performed during the same penetration process, which eliminates the need to relocate equipment and reduces the labor required for measurement work.

[0021] As the present invention according to claim 6, there is provided a test method for confirming the effect of ground improvement as described in claim 5, in which the reliability of the electrical logging is evaluated by comparing the resistivity values ​​of the electrical logging when the hammer strikes the dynamic cone penetration test and when it is stopped.

[0022] In the invention described in claim 6 above, in order to ensure the reliability of electrical logging even when poor contact between the electrode and the hole wall occurs due to the vibration of the measurement probe during penetration by hammer striking in a dynamic cone penetration test, it is confirmed that there is no difference in the resistivity value of electrical logging when the hammer strikes and when it is stopped. [Effects of the Invention]

[0023] As explained above in detail, the present invention can provide a test device and a test method for confirming the effect of ground improvement, which does not require the relocation of equipment and reduces the labor required for measurement work. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view showing a test device 1 according to the present invention. [Figure 2] 1A and 1B show a measurement probe 3, in which (A) is a front view and (B) is a side view. [Figure 3] FIG. 2 is an exploded view of the measurement probe 3. [Figure 4] 1A and 1B show a measurement probe main body 8, in which (A) is a front view and (B) is a side view. [Figure 5] This is a depth distribution map of electrical resistivity values ​​at the time of penetration and extraction. [Figure 6] This is a comparison of electrical resistivity values ​​during penetration and extraction. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0026] The present invention is a test device 1 for confirming the effectiveness of ground improvement using a chemical injection method in which chemicals such as water glass (sodium silicate) or cement-based ground injection materials are injected into the ground to strengthen soft ground such as reclaimed land.

[0027] As shown in Figure 1, the testing device 1 of the present invention is a device that measures ground properties by attaching a measurement probe 3 to the tip of a penetration rod 2, striking an anvil 20 fixed to the penetration rod 2 in the axial direction with a hammer 21, and penetrating the measurement probe 3 into the ground.

[0028] As shown in Figure 2, the measurement probe 3 has a tip cone 4 used for dynamic cone penetration testing at its tip, and an electrode section 5 with an electrode 6 used for electrical logging on its outer surface is provided on top of the tip cone 4.

[0029] The outer diameter of the electrode portion 5 is smaller than that of the tip cone 4. The axis of the tip cone 4 and the axis of the electrode portion 5 are eccentric, and the electrode 6 is disposed on the outer peripheral surface of the electrode portion 5 on the eccentric side.

[0030] As shown in FIG. 1, this testing device 1 is capable of performing a dynamic cone penetration test and electrical logging simultaneously during the penetration process of the measurement probe 3.

[0031] The dynamic cone penetration test can be performed using various sounding methods such as the standard penetration test, Swedish penetration test, ram sounding, and small dynamic cone penetration test, but preferably a large or medium-sized ram sounding (SRS, MRS) is used. Also, any known operating method can be used, such as fully automatic, semi-automatic, or manual. Therefore, the test device 1 according to the present invention can be used for a variety of ground conditions.

[0032] To perform a dynamic cone penetration test using this testing device 1, as shown in Figure 1, an anvil 20 fixed to a penetration rod 2 is struck in the axial direction with a hammer 21 with a predetermined striking force, driving the tip cone 4 into the ground, and the penetration amount and number of strikes are measured. The tip cone 4 penetrates to the required depth by sequentially adding segments of the penetration rod 2, which are divided into predetermined lengths.

[0033] The electrical logging uses the electrode 6 attached to the electrode unit 5 of the measurement probe 3 to measure the electrical resistance (resistivity) of the surrounding ground and confirm the effectiveness of ground improvement. The progress of improved soils created by the chemical grouting method is generally managed using the uniaxial compressive strength (qu). However, the target strength of the improved soil is not particularly high, at around qu = 50 to 100 kPa. This results in large variations in strength due to disturbances caused by sampling and uneven soil conditions, making it difficult to quantitatively grasp changes in properties before and after improvement. Therefore, measuring electrical resistivity is effective in quantitatively grasping property values ​​that are more sensitive than strength.

[0034] The measurement probe 3 will be described in more detail below. The measurement probe 3 has a rod-like appearance that is elongated in the vertical direction and has a generally circular cross section, and an external thread 8a is formed at the upper end for connection to the penetration rod 2, and is capable of threadably connecting to an internal thread provided at the lower end of the penetration rod 2. An electrode section 5 is provided below the external thread 8a, in which a plurality of electrodes 6 are arranged in a row at predetermined positions in the circumferential direction with intervals in the axial direction, and the tip cone 4 is disposed below this electrode section 5 at the lower end of the measurement probe 3.

[0035] As shown in Figure 3, the measurement probe 3 is composed of a measurement probe main body 8 connected to the penetration rod 2, an outer sleeve 9 fitted onto the measurement probe main body 8 at a position corresponding to the electrode portion 5, an eccentric spacer 10 fitted onto the lower end of the measurement probe main body 8, and a tip cone 4 fitted onto the eccentric spacer 10.

[0036] 4, the measurement probe body 8 is a vertically elongated rod-shaped member with a generally circular cross section made of a metal or the like having the strength to transmit the axial impact force input to the penetration rod 2 during a dynamic cone penetration test to the tip cone 4 at the lower end, and has a hollow section formed over the axial section from the upper end to at least the part where the electrode 6 is disposed. A male thread 8a that screws into the penetration rod 2 is formed at the upper end.

[0037] The lower end of an electric cable 7 is connected to each electrode 6 and is wired from the upper opening of the measurement probe body 8 through the hollow portion. The upper end of the electric cable 7 passes through the hollow portion of the penetration rod 2, which has a hollow cylindrical cross section, over its entire length and extends to the ground, and its tip is connected to a computer 19 (see FIG. 1) that records and analyzes measurement data, and a power supply (not shown).

[0038] In addition, one or more ring-shaped water-stopping members 11 are provided on the outer peripheral surface above and below the axial section in which the electrodes 6 of the measurement probe body 8 are arranged, in order to prevent groundwater and the like from entering through the gap between the outer sleeve 9 (Figure 3).

[0039] Furthermore, a groove that runs along the axial direction and communicates with the inside of the hollow section from the outside is provided on part of the outer circumferential surface of the axial section of the measurement probe main body 8 where the electrode 6 is arranged, and an insulating member 12 made of an electrically insulating material such as resin is fitted into this groove. The electrode 6 is provided so as to penetrate the outer and inner surfaces of this insulating member 12.

[0040] The electrodes 6 may be arranged in a two-pole or three-pole manner, but a four-pole manner is preferred. In the four-pole electrode arrangement, as shown in Figures 2 to 4, four electrodes 6 are arranged in a row in the vertical direction (axial direction) at a predetermined interval, with the two electrodes 6A at both ends in the vertical direction and the two electrodes in the middle being potential electrodes 6V. The center-to-center distance between adjacent electrodes is preferably 2.5 cm. The use of the four-pole method has the advantage of eliminating the need for a ground electrode and stabilizing measured values.

[0041] The electrodes 6 are made of a conductive metal material and are provided so as to electrically communicate from the hollow interior of the measurement probe main body 8 to the outer circumferential surface of the measurement probe 3. The electrodes 6 are connected to the lower ends of electric cables 7 in the hollow interior of the measurement probe main body 8, respectively.

[0042] The electrode section 5 is configured by fitting an outer sleeve 9 having a plurality of electrodes 6 exposed on the outer peripheral surface onto a measurement probe main body 8 connected to the penetration rod 2. The electrodes 6 provided on this outer sleeve 9 are provided penetrating the outer peripheral surface and the inner peripheral surface of the outer sleeve 9, and are arranged in a row at intervals in the axial direction, similar to the electrodes 6 provided on the measurement probe main body 8. When the outer sleeve 9 is attached to the measurement probe main body 8, each electrode 6 provided on the outer sleeve 9 is electrically connected to the corresponding electrode 6 provided on the measurement probe main body 8.

[0043] The outer sleeve 9 is made of an electrically insulating material such as resin and is a substantially cylindrical member with both axial ends open. As shown in FIG. 2 , when the outer sleeve 9 is inserted into the measurement probe main body 8, its outer diameter is larger than the outer diameter of the measurement probe 3 (measurement probe main body 8) located above the electrode unit 5. By making the outer diameter of the outer sleeve 9 larger than the outer diameter of the measurement probe 3 located above the electrode unit 5, the electrode 6 exposed on the outer peripheral surface of the outer sleeve 9 is more likely to come into contact with the hole wall surface when the measurement probe 3 is inserted into the ground, improving the measurement accuracy of electrical logging and reducing damage to the measurement probe 3.

[0044] The outer diameter of the outer sleeve 9 (electrode portion 5) is smaller than the outer diameter of the tip cone 4. This allows the penetration resistance of the tip cone 4 to be measured primarily during a dynamic cone penetration test, minimizing the effect of friction on the circumferential surface of the outer sleeve 9 (electrode portion 5). The difference between the outer diameter of the electrode portion 5 and the outer diameter of the tip cone 4 is preferably 2 to 10 mm.

[0045] The outer sleeve 9 is inserted from the outer surface side into through holes provided in the outer sleeve 9, and is fixed by a plurality of flat head screws 14 that are threaded into screw holes provided in the measurement probe main body 8 so that relative axial displacement and circumferential rotation do not occur with respect to the measurement probe main body 8. With the outer sleeve 9 fixed by the plurality of flat head screws 14, the electrodes 6 provided in the measurement probe main body 8 and the electrodes 6 provided in the outer sleeve 9 can be aligned, and circumferential rotation of the measurement probe main body 8 and the outer sleeve 9 can be prevented, so that misalignment does not occur between the electrodes 6 provided in the measurement probe main body 8 and the electrodes 6 provided in the outer sleeve 9 when the measurement probe 3 is inserted or removed.

[0046] 2(B), the measurement probe 3 has an eccentric axis of the tip cone 4 and an eccentric axis of the electrode unit 5, and the electrode 6 is disposed on the outer circumferential surface of the electrode unit 5 on the side where the axis of the electrode unit 5 is eccentric with respect to the axis of the tip cone 4. Here, the axis of the tip cone 4 and the axis of the electrode unit 5 are eccentric to the extent that the outer circumferential surface of the electrode unit 5 does not protrude radially outward from the outer circumferential surface of the tip cone 4. This reduces the circumferential friction of the electrode unit 5 in a dynamic cone penetration test, and makes it possible to reliably bring the electrode 6 of the electrode unit 5 into contact with the hole wall surface during electrical logging.

[0047] As shown in Figure 2(B), the diametric separation distance S between the outer circumferential surface of the tip cone 4 and the outer circumferential surface of the electrode unit 5 on the eccentric side of the electrode unit 5 is preferably 0 to 3 mm. This reduces peripheral friction during the dynamic cone penetration test, and enables electrical logging by ensuring that the electrode 6 of the electrode unit 5 is in reliable contact with the hole wall surface.

[0048] As shown in FIG. 3, an eccentric spacer 10 is fitted onto the lower end of the measurement probe body 8, and the tip cone 4 is fitted onto the eccentric spacer 10.

[0049] The eccentric spacer 10 is a sleeve member made of resin or metal and formed in a generally cylindrical shape with both axial ends open, with a flange-like eccentric collar 16 formed at the upper end (base end). The eccentric spacer 10 is fixed to the measurement probe body 8 by a non-detachable fixing means so that it does not fall off from the measurement probe body 8 when the measurement probe 3 is inserted or removed. Examples of such fixing means include welding or mechanical element connection to the measurement probe body 8 using screws, pins, rivets, etc.

[0050] The eccentric spacer 10 is fixed so that there is no relative rotation or axial displacement with respect to the measurement probe main body 8, by having an embedded screw threaded from the outer surface into a threaded hole provided on the circumferential surface of the eccentric spacer 10, and the tip of the embedded screw fitting into a set screw recess 17 (see Figure 4) provided on the measurement probe main body 8.

[0051] The axial center of the inner peripheral surface of the eccentric spacer 10 coincides with the axial center of the measurement probe main body 8, while the axial center of the outer peripheral surface is eccentric with respect to the axial center of the measurement probe main body 8. As a result, when the eccentric spacer 10 is fitted onto the outside of the measurement probe main body 8 and the tip cone 4 is further fitted onto the outside of this eccentric spacer 10, the axial centers of the measurement probe main body 8 and the tip cone 4 become eccentric.

[0052] The tip cone 4 is not fixed to the eccentric spacer 10, but is simply fitted onto the outside of the eccentric spacer 10. Therefore, when the measurement probe 3 is pulled out after being penetrated into the ground, the tip cone 4 falls off the measurement probe 3 and is left at the bottom of the hole.

[0053] The tip cone 4 is used in a shape and size that conforms to the specifications of various dynamic cone penetration tests. The outer diameter of the tip cone 4 is larger than the outer diameter of the electrode portion 5 so that the resistance during penetration in the dynamic cone penetration test acts on the tip cone 4. If the tip cone 4 were larger in diameter than the electrode portion 5 and the axis of the tip cone were aligned with the axis of the electrode portion, the electrode would not contact the hole wall, making it impossible to perform accurate electrical logging. However, in the measurement probe 3 of the present invention, the axis of the tip cone 4 and the axis of the electrode portion 5 are eccentric, and the electrode is located on the outer peripheral surface of the eccentric side. This allows the electrode to contact the hole wall during the penetration of the measurement probe 3, enabling accurate electrical logging. In this case, the contact portion of the electrode portion 5 with the hole wall is linear, thereby reducing peripheral friction during the penetration process of the dynamic cone penetration test.

[0054] As shown in FIG. 2 , the measurement probe body 8 at the portion where the upper end of the outer sleeve 9 abuts is provided with an inclined step 18, which is a step formed obliquely in the circumferential direction between the outer peripheral surface of the measurement probe body 8 and the outer peripheral surface of the outer sleeve 9. The inclined step is highest in the vertical direction at the circumferential position where the electrode 6 is located and lowest on the opposite side. The step surface itself forms a radially inclined surface along the entire circumference, which is higher toward the radial center and gradually lowers toward the periphery. By forming such an inclined step 18 at the boundary with the outer sleeve 9, sediment that accumulates in the step can be efficiently removed to the periphery when the measurement probe 3 is withdrawn, making the operation easier.

[0055] As shown in Figure 3, the assembly of the measurement probe 3 is completed by attaching the electrode 6 and electrical cable 7 to the measurement probe main body 8, and then attaching the water-stopping member 11, and then inserting the outer sleeve 9 and eccentric spacer 10 in that order from the lower end side of the measurement probe main body 8, and fixing the eccentric spacer 10 to the measurement probe main body 8, and finally fitting the tip cone 4 onto the eccentric spacer 10.

[0056] To conduct a test to confirm the effect of ground improvement using the test device 1 configured as described above, as shown in Figure 1, a dynamic cone penetration test is performed in which the tip cone 4 is driven into the ground by striking it with a hammer 21 while the penetration rod 2 and electrical cable 7 are successively added, and at the same time, electrical logging is performed at predetermined intervals during the same penetration process in which a current is passed through the current electrode 6A and the resulting potential difference is measured with the potential electrode 6V.

[0057] In this way, in the present invention, during the penetration process of the measurement probe 3, a dynamic cone penetration test is performed and electrical logging is also performed at the same time, which eliminates the need to change the equipment installation between the dynamic cone penetration test and electrical logging, thereby reducing the labor required for measurement work.

[0058] The measurement interval for the electrical logging is preferably 0.5 to 5 Hz. That is, a current is passed through the current electrode 6A at intervals of 0.2 to 2 seconds, and the resulting potential difference is measured by the potential electrode 6V. By performing electrical logging at this measurement interval, data errors caused by poor contact due to vibrations during dynamic penetration do not occur, allowing for stable electrical logging.

[0059] It is also preferable to evaluate the reliability of the electrical logging by comparing the resistivity values ​​of the electrical logging when the hammer strikes and when the test is stopped during the dynamic cone penetration test. That is, data errors are verified by confirming that there is no significant difference in the resistivity values ​​when the hammer strikes and when the test is stopped. When the resistivity values ​​when the hammer strikes and when the test is stopped are within a range of ±10%, preferably ±5%, it can be determined that there is no difference in the resistivity values.

[0060] The effectiveness of the ground improvement is confirmed by using the test device 1 to perform dynamic cone penetration tests and electrical logging before and after the ground improvement, and comparing the depth distribution map of the N value or Nd value before and after the ground improvement obtained by the dynamic cone penetration test with the decrease in resistivity before and after the ground improvement obtained by the electrical logging. [Example]

[0061] A test device 1 was created by modifying an existing fully automatic ram sounding survey machine used for dynamic cone penetration tests, which is also capable of electrical logging. A demonstration experiment was conducted in which electrical logging was performed simultaneously with the dynamic cone penetration test during the penetration process, verifying the feasibility of electrical logging during the penetration process.

[0062] In the experiment, electrical logging was also carried out when the measurement probe 3 was withdrawn, and the results were compared with the resistivity value at the time of penetration.

[0063] The electrical logging is outlined below: Current value (measurement range): 0.1 to 20 mA (auto), measurement resistance: 0 to 1999 Ωm, data sampling interval: 1 to 5 Hz The results of electrical logging during penetration and withdrawal are shown in Figures 5 and 6. As a result, the results of electrical logging during penetration and withdrawal were almost identical, verifying that accurate measurement data can be obtained even when electrical logging is performed simultaneously with a dynamic cone penetration test during the penetration process. [Explanation of symbols]

[0064] 1...Test device, 2...Penetration rod, 3...Measuring probe, 4...Tip cone, 5...Electrode portion, 6...Electrode, 7...Electrical cable, 8...Measuring probe body, 9...Outer sleeve, 10...Eccentric spacer, 11...Watertight member, 12...Insulating member, 14...Countersunk head screw, 16...Eccentric flange portion, 17...Recess for set screw, 18...Sloped step portion

Claims

1. A test device for confirming the effect of ground improvement, in which a measurement probe is attached to the tip of a penetration rod, The measurement probe has a tip cone used for a dynamic cone penetration test at its tip, and an electrode portion having an electrode used for electrical logging on its outer peripheral surface is provided on the top of the tip cone, an outer diameter of the electrode portion is smaller than an outer diameter of the tip cone, an axis of the tip cone and an axis of the electrode portion are eccentric, and the electrode is disposed on the outer peripheral surface of the eccentric side; This test equipment is designed to verify the effectiveness of ground improvement by simultaneously conducting dynamic cone penetration tests and electrical logging during the penetration process.

2. A test device for confirming the effect of ground improvement as described in claim 1, wherein the axis of the tip cone and the axis of the electrode part are eccentric to the extent that the outer surface of the electrode part does not protrude radially outward from the outer surface of the tip cone.

3. A test device for confirming the effect of ground improvement as described in claim 1, wherein the diametric distance between the outer surface of the tip cone and the outer surface of the electrode portion on the eccentric side of the electrode portion is 0 to 3 mm.

4. 2. A test device for confirming the effect of ground improvement according to claim 1, wherein the measurement interval of the electrical logging is 0.5 to 5 Hz.

5. A test method for confirming the effect of ground improvement using the test device according to any one of claims 1 to 4, A test method for confirming the effectiveness of ground improvement, characterized in that a dynamic cone penetration test is conducted in which the tip cone is driven into the ground by hammering, and electrical logging is also conducted during the same penetration process.

6. A test method for confirming the effect of ground improvement as described in claim 5, in which the reliability of the electrical logging is evaluated by comparing the resistivity values ​​of the electrical logging when the hammer is struck and when the dynamic cone penetration test is stopped.

Images